[PATCH] mm: VM_BUG_ON

Introduce a VM_BUG_ON, which is turned on with CONFIG_DEBUG_VM.  Use this
in the lightweight, inline refcounting functions; PageLRU and PageActive
checks in vmscan, because they're pretty well confined to vmscan.  And in
page allocate/free fastpaths which can be the hottest parts of the kernel
for kbuilds.

Unlike BUG_ON, VM_BUG_ON must not be used to execute statements with
side-effects, and should not be used outside core mm code.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Christoph Lameter <clameter@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 12 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 8a52ba9fe693..4b33878e9488 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -127,7 +127,6 @@ static int bad_range(struct zone *zone, struct page *page)
 
         return 0;
 }
-
 #else
 static inline int bad_range(struct zone *zone, struct page *page)
 {
@@ -218,12 +217,12 @@ static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags)
 {
         int i;
 
-        BUG_ON((gfp_flags & (__GFP_WAIT | __GFP_HIGHMEM)) == __GFP_HIGHMEM);
+        VM_BUG_ON((gfp_flags & (__GFP_WAIT | __GFP_HIGHMEM)) == __GFP_HIGHMEM);
         /*
          * clear_highpage() will use KM_USER0, so it's a bug to use __GFP_ZERO
          * and __GFP_HIGHMEM from hard or soft interrupt context.
          */
-        BUG_ON((gfp_flags & __GFP_HIGHMEM) && in_interrupt());
+        VM_BUG_ON((gfp_flags & __GFP_HIGHMEM) && in_interrupt());
         for (i = 0; i < (1 << order); i++)
                 clear_highpage(page + i);
 }
@@ -347,8 +346,8 @@ static inline void __free_one_page(struct page *page,
 
         page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1);
 
-        BUG_ON(page_idx & (order_size - 1));
-        BUG_ON(bad_range(zone, page));
+        VM_BUG_ON(page_idx & (order_size - 1));
+        VM_BUG_ON(bad_range(zone, page));
 
         zone->free_pages += order_size;
         while (order < MAX_ORDER-1) {
@@ -421,7 +420,7 @@ static void free_pages_bulk(struct zone *zone, int count,
         while (count--) {
                 struct page *page;
 
-                BUG_ON(list_empty(list));
+                VM_BUG_ON(list_empty(list));
                 page = list_entry(list->prev, struct page, lru);
                 /* have to delete it as __free_one_page list manipulates */
                 list_del(&page->lru);
@@ -512,7 +511,7 @@ static inline void expand(struct zone *zone, struct page *page,
                 area--;
                 high--;
                 size >>= 1;
-                BUG_ON(bad_range(zone, &page[size]));
+                VM_BUG_ON(bad_range(zone, &page[size]));
                 list_add(&page[size].lru, &area->free_list);
                 area->nr_free++;
                 set_page_order(&page[size], high);
@@ -761,8 +760,8 @@ void split_page(struct page *page, unsigned int order)
 {
         int i;
 
-        BUG_ON(PageCompound(page));
-        BUG_ON(!page_count(page));
+        VM_BUG_ON(PageCompound(page));
+        VM_BUG_ON(!page_count(page));
         for (i = 1; i < (1 << order); i++)
                 set_page_refcounted(page + i);
 }
@@ -809,7 +808,7 @@ again:
         local_irq_restore(flags);
         put_cpu();
 
-        BUG_ON(bad_range(zone, page));
+        VM_BUG_ON(bad_range(zone, page));
         if (prep_new_page(page, order, gfp_flags))
                 goto again;
         return page;
@@ -1083,7 +1082,7 @@ fastcall unsigned long get_zeroed_page(gfp_t gfp_mask)
          * get_zeroed_page() returns a 32-bit address, which cannot represent
          * a highmem page
          */
-        BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
+        VM_BUG_ON((gfp_mask & __GFP_HIGHMEM) != 0);
 
         page = alloc_pages(gfp_mask | __GFP_ZERO, 0);
         if (page)
@@ -1116,7 +1115,7 @@ EXPORT_SYMBOL(__free_pages);
 fastcall void free_pages(unsigned long addr, unsigned int order)
 {
         if (addr != 0) {
-                BUG_ON(!virt_addr_valid((void *)addr));
+                VM_BUG_ON(!virt_addr_valid((void *)addr));
                 __free_pages(virt_to_page((void *)addr), order);
         }
 }